WASHINGTON – Robert Novak, the aggressive reporter and conservative commentator who became a television celebrity, died Tuesday of brain cancer at the age of 78.

For three decades, from Presidents John F. Kennedy to Bill Clinton, Novak and partner Rowland Evans wrote a syndicated column about the inner workings of Washington; Novak then did the column solo until he fell ill last year.

After CNN debuted in 1980, the acerbic Novak became a fixture on such programs as “Crossfire,” in which he battled verbally with liberal foes.

“I tried to find out what the politicians were up to, which is a difficult job,” Novak told Washingtonian magazine after he stopped his column in November. “I find that politicians as a class are up to no good. Sometimes they accidentally do the right thing.”

A journalist dubbed Novak “the prince of darkness”; he used the phrase as the title of his 2007 memoir.

Near the end of his career, Novak triggered a federal investigation of the George W. Bush administration when he published the name of CIA operative Valerie Plame Wilson in July 2003. The column appeared after her husband and former diplomat Joseph Wilson challenged the rationale behind the Iraq war. Novak – who opposed the invasion of Iraq – was never charged with wrongdoing.

CNN refused to let him back on the air after he stalked off the set during a 2005 debate with Democratic consultant James Carville. Novak finished his television career with Fox News.

Born Feb. 26, 1931, in Joliet, Ill., Novak was a newspaper reporter while in high school and at the University of Illinois. He later reported for the Associated Press before going to the Wall Street Journal in 1958.

In 1963, Evans asked Novak to be his partner. The Evans-Novak column ran 30 years and often enraged politicians.

Bill Press, a “proud liberal” who co-hosted “Crossfire” with Novak for six years, said they became friends because they respected each other’s principles. He called Novak the hardest-working reporter in Washington who “had sources because he worked them, he thanked them, and he never double-crossed them.”